Evolution of Photospheric Magnetic Fields associated with Solar Flares

Haimin Wang

Big Bear Solar Observatory, New Jersey Institute of Technology

Evolution of magnetic fields is clearly associated with flares. The following topics will be discussed: (1) Magnetic evolution that may lead to flares such as high magnetic gradient, strong magnetic shear, large twist and electric current, new flux emergence, helicity injection and shear/converging flows. (2) Rapid changes of magnetic fields and flow patterns before and after flares. New observational evidence supports magnetic reconnection stipulated by the tether cutting model.